Bone marrow stromal cells (MSC), which represent a population of multipotential mesenchymal stem cells, have been reported to undergo rapid and robust transformation into neuron-like phenotypes in vitro following treatment with chemical induction medium including dimethyl sulfoxide (DMSO; Woodbury et al. [2002] J. Neurosci. Res. 96:908). In this study, we confirmed the ability of cultured rat MSC to undergo in vitro osteogenesis, chondrogenesis, and adipogenesis, demonstrating differentiation of these cells to three mesenchymal cell fates. We then evaluated the potential for in vitro neuronal differentiation of these MSC, finding that changes in morphology upon addition of the chemical induction medium were caused by rapid disruption of the actin cytoskeleton. Retraction of the cytoplasm left behind long processes, which, although strikingly resembling neurites, showed essentially no motility and no further elaboration during time-lapse studies. Similar neurite-like processes were induced by treating MSC with DMSO only or with actin filament-depolymerizing agents. Although process formation was accompanied by rapid expression of some neuronal and glial markers, the absence of other essential neuronal proteins pointed toward aberrantly induced gene expression rather than toward a sequence of gene expression as is required for neurogenesis. Moreover, rat dermal fibroblasts responded to neuronal induction by forming similar processes and expressing similar markers. These studies do not rule out the possibility that MSC can differentiate into neurons; however, we do want to caution that in vitro differentiation protocols may have unexpected, misleading effects. A dissection of molecular signaling and commitment events may be necessary to verify the ability of MSC transdifferentiation to neuronal lineages.

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This study evaluates functional recovery after transplanting human bone marrow-derived stromal cells (BMSCs) into contusion models of spinal cord injury (SCI). The authors used a high-throughput process to expand BMSCs and characterized them by flow cytometry, ELISA, and gene expression. They found that BMSCs secrete neurotrophic factors and cytokines with therapeutic potential for cell survival and axon growth. In adult immune-suppressed rats, mild, moderate, or severe contusions were generated using the MASCIS impactor. One week following injury, 0.5 to 1 x 106 BMSCs were injected into the lesioned spinal cord; control animals received vehicle injection. Biweekly behavioral tests included the Basso, Beattie, and Bresnahan Locomotor Rating Scale (BBB), exploratory rearing, grid walking, and thermal sensitivity. Animals receiving moderate contusions followed by BMSC grafts showed significant behavioral recovery in BBB and rearing tests when compared to controls. Animals receiving BMSC grafts after mild or severe contusion showed trends toward improved recovery. Immunocytochemistry identified numerous axons passing through the injury in animals with BMSC grafts but few in controls. BMSCS were detected at 2 weeks after transplantation; however, at 11 weeks very few grafted cells remained. The authors conclude that BMSCs show potential for repairing SCI. However, the use of carefully characterized BMSCs improved transplantation protocols ensuring BMSC, survival, and systematic motor and sensory behavioral testing to identify robust recovery is imperative for further improvement.

Objective-Bone marrow stromal cells (MSC) are multipotent adult stem cells that have emerged as promising candidates for cell therapy in disorders including cardiac infarction, stroke and spinal cord injury. While harvesting methods used by different laboratories are relatively standard, MSC culturing protocols vary widely. This study is aimed at evaluating the effects of initial plating density and total time in culture on proliferation, cell morphology, and differentiation potential of heterogeneous MSC cultures and more homogeneous cloned subpopulations.Methods-Rat MSC were plated at 20, 200 and 2000 cells/cm 2 and grown to 50% confluency. The numbers of population doublings and doubling times were determined within and across multiple passages. Changes in cell morphology and differentiation potential to adipogenic, chondrogenic, and osteogenic lineages were evaluated and compared among early, intermediate and late passages, as well as between heterogeneous and cloned MSC populations.Results-We found optimal cell growth at a plating density of 200 cells/cm 2 . Cultures derived from all plating densities developed increased proportions of flat cells over time. Assays for chondrogenesis, osteogenesis and adipogenesis showed that heterogeneous MSC plated at all densities sustained the potential for all three mesenchymal phenotypes through at least passage 5; the flat subpopulation lost adipogenic and chondrogenic potential.Conclusion-Our findings suggest that the initial plating density is not critical for maintaining a well-defined, multipotent MSC population. Time in culture, however, affects cell characteristics, suggesting that cell expansion should be limited, especially until the specific characteristics of different MSC subpopulations are better understood. Keywordsadult stem cells; heterogeneity; variability; differentiation potential; expansion Bone marrow stromal cells (MSC) represent a heterogeneous population derived from the nonblood forming fraction of bone marrow that regulates hematopoietic cell development. In vitro, adult mesenchymal stem cells resident in this bone marrow fraction differentiate into bone, cartilage and fat (1). Cultured MSC have also been shown to regenerate cardiac (2) and Correspondence: Birgit Neuhuber, Ph.D, Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129, Phone: (215) Fax: (215) 843-9803, E-mail: bneuhuber@drexelmed.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. In this study, we cultured rat MSC for which no effort was made to limit heterogene...

Voltage-sensitive calcium channels are multimeric protein complexes formed by the á1 subunit and the auxiliary subunits áµä, â and ã (Leung et al. 1987;Takahashi et al. 1987;Vaghy et al. 1987). The á1 subunit by itself shows the characteristic properties of a voltage-gated ion channel, i.e. voltage sensing, ion permeation and drug binding. The physiological roles of the auxiliary subunits are currently the subject of intensive investigations. The â subunit modulates calcium currents by increasing the current density and by changing the current kinetics when coexpressed in heterologous expression systems (Lacerda et al. 1991;Varadi et al. 1991;Lory et al. 1992). Furthermore, it has been suggested that the â subunit is involved in the targeting of the á1 subunit to the plasma membrane (Chien et al. 1995; Gregg et al. 1996). Both the á1 and â subunits exist in multiple tissue-specific isoforms, which differ from one another in their primary structure and in their functional properties (Birnbaumer et al. 1994;Isom et al. 1994). The skeletal muscle á1S isoform, for example, shows slow activation and inactivation kinetics compared with the other á1 isoforms. Also, whereas á1C expressed in heterologous expression systems exhibits currents even in the absence of auxiliary subunits (Perez-Garcia et al. 1995), expression of á1S in heterologous systems rarely gives rise to measurable calcium currents (Johnson et al. 1997). The â subunit isoforms differ in their current modulation (Hullin et al. 1992;Sather et al. 1993;Parent et al. 1997) and, when expressed alone, in their subcellular distribution (Chien et al. 1995(Chien et al. , 1996Brice et al. 1997). For example, â2a drastically reduced the speed of inactivation when coexpressed with the neuronal á1E subunit in oocytes (Parent et al. 1997), whereas other â subunit isoforms showed only minor effects on current inactivation. Analogously, â2a differs from most other â isoforms in that it was localized in the plasma membrane when expressed without an á1 subunit in a heterologous expression system (Chien et al. 1995), whereas